In order to study the influence of loading conditions on propellant mesoscopic failure morphology, scanning electron microscopy was carried out to observe the morphology of the failure section of a hydroxyl-terminated polybutadiene propellant under different temperatures, loading speeds, and loading conditions. Using the finite element method, a mesoscopic model of a composite solid propellant was constructed, and the mechanical parameters of the propellant particle–matrix interface were obtained based on the parameter inversion method. A meso-model of a hydroxyl-terminated polybutadiene propellant under different loading conditions was constructed, and numerical results were compared with experimental results to analyze the meso-damage. With decreasing temperature and increasing loading speed, the level of propellant damage increased, and the particle–matrix interface became more prone to damage under the combined action of tensile and shear loads. In addition, with an increasing loading angle, ammonium perchlorate particles were more prone to dewetting.

Due to strategic requirements, tactical missiles need to be transported several times before they are launched. For this reason, this study examined the cumulative damage that occurs in a solid rocket motor grain during road transportation. Constant-stress reciprocating tensile tests of a composite solid propellant were designed and carried out, and the characteristic fatigue curve of the propellant was fitted and analyzed. By processing power spectral density data for equipment transportation tests, a vibration acceleration load spectrum for a solid rocket motor grain in the process of highway transportation was obtained. A three-dimensional finite-element calculation model of a solid rocket motor was established, and the stress response of the motor grain was simulated. After this, cyclic loads were obtained using a rainflow counting method. The cumulative damage to the solid rocket motor grain during highway transportation was calculated according to Miner’s linear cumulative-damage model and evaluated. It was concluded that during transportation, the maximum stress of the solid rocket motor is 0.2 MPa, the maximum strain is 0.03, and the maximum displacement is 19.32 mm, all of which are found in the front stress-release boot. After 4000 km driving on the highway, the damage to the front stress-release boot of the grain is thus the greatest, with a value of 0.0796. The damage to the inner hole of the grain was found to be the smallest, with a value of 0.0438.